Vertebrate
fauna

(mostly from Foster [2003], with additional material in the
mammal section after [1]; the
higher-level classifications will vary as new finds are made. Only
described taxa are included, so several Nomina nuda and undescribed taxa are
left out)

Amphibians

According to museum curator John Foster, "frogs are known from
several sites in the Morrison Formation but are not particularly
well represented."[1]
The history of Morrison anuran discoveries began with the recovery
of remains from Reed's Quarry 9 near Como Bluff Wyoming. The new
genus Eobatrachus was erected for some of these remains by
O. C. Marsh, but the material was later considered non-diagnostic.
Decades later another dubious anuran genus, Comobatrachus
was erected for addition fragmentary remains. Despite the erection
of multiple new names, scientists only recognize two legitimate
frog species from the Morrison, Enneabatrachus hechti[2]
and Rhadinosteus parvus.[3]

By the late Morrison, gigantic diplodocids (or likely
diplodocids) had appeared, including Diplodocus hallorum
(formerly Seismosaurus), Supersaurus vivianae, Amphicoelias
altus, and the largest of all, A. fragilimus.
Smaller sauropods, such as Suuwassea emiliae from Montana, tend to be found in
the northern reaches of the Morrison, near the shores of the
ancient Sundance
Sea, suggesting ecological niches favoring smaller body size
there compared with the giants found further south.[8]

Camarasaurs reached an adult size of about
18 m in length.[9
] A Camarasaurus pelvis from the
Cleveland-Lloyd Quarry shows evidence of gouging that has been
attributed to Allosaurus. A juvenile specimen was
recovered from Dinosaur National Monument in Utah.[9
]

A large, robust megalosaurid reaching lengths of up to
11 m. One of the largest carnivores of the formation.

Fish

Although the paleoclimate of the Morrison formation was semiarid
with only seasonal rainfall, there were enough bodies of water to
support a diverse ichthyofauna.[10]
Although abundant, fish remains are constrained to only certain
locations within the formation.[10]
Microvertebrate sites in Wyoming are dominated by fish remains.[10]

Tooth plates from Saltwash to upper Brushy Basin Member found
in many areas of the formation. Found in stratigraphic zones
2-6.[4]

A lungfish genus whose members ranged from 1 to 2 m in
length and weights of up to 79 pounds.[10]
However most Morrison lungfish would have been on the smaller side
of that range.[10]
These species are believed to have had similar diets to extant
lungfish.[10]
The modern lungfish Neoceratodus is
physically very similar to Ceratodus.[10]

Geographically present in the western part of Colorado, where
remains have been recovered from "a level above the Mygatt-Moore
Quarry."[10]

Known only from a single nearly complete skeleton found at
Rabbit Valley, Colorado.[11]
Found in stratigraphic zone 5.[4]

Largely complete remains of small individuals have been
consistently recovered for over 15 years.[10]

A 13 cm (5 inch) fish that was deeper bodied than its
co-occurring contemporaries Morrolepis and
Hulettia.[11]
The Morrison cf. Leptolepis probably had a live mass of
about 37g.[11]
It is the only teleost fish known from the formation and was
morphologically more highly derived than other Morrison fish.[11]
It is believed to have fed on contemporary fish and small
invertebrates.[11]

A palaeoniscoid with forward-set eyes positioned past the front
end of the lower jaw. It had a tall dorsal fin set far back on the
body and an asymmetrical caudal fin.[12]
Adult specimens would reach about 20 cm in length and 113 g
(4oz) in mass.[12]

The first specimen was nearly complete, the four subsequent
findings vary in completeness.[12]

In 2009, a study by J. R. Foster was
published which estimated the body masses of mammals from the
Morrison Formation by using the ratio of dentary length
to body mass of modern marsupials as a reference. Foster concludes
that Docodon was
the most massive mammal genus of the formation at 141g and Fruitafossor was
the least massive at 6g. The average Morrison mammal had a mass of
48.5g. A graph of the body mass distribution of Morrison mammal
genera produced a right-skewed
curve, meaning that there were more low-mass genera.[14]

Sites where fossils are found include Carnegie Quarry and
Rainbow Park areas at Dinosaur National Monument as well as the
Fruita Paleontological Area, Wolf Creek Quarry, the Uravan
Locality, and the Kings View Quarry.

Pterosaurs

Pterosaurs are very
uncommon fossils in the Morrison, because the fragility of their
thin walled bones often prevented their remains from being
preserved.[18]
Despite being uncommon they are geographically widespread;[19]
indeterminate pterosaur remains have been found in stratigraphic
zones 2 and 4-6.[4]
In addition to indeterminate remains, several species have been
identified from both the rhamphorhynchoids (long-tailed
pterosaurs) and pterodactyloids (short-tailed
pterosaurs).[18]
Since the 1970s and 80s, pterosaur finds have become more common,
but are still rare.[18]
Most Morrison pterosaurs have been found in marine and shoreline
deposits.[18]
Pterosaur tracks have been found in both the Tidwell and Saltwash
members.[18]
Morrison pterosaurs probably lived on fish, insects and scavenged
dinosaur carcasses.[18]

The first known remains were recovered from a coarse sandstone
deposit in the Dry Mesa Quarry.[22]
Later remains referred to Mesadactylus were recovered from
the Kingsview Quarry.[22]
So far all known Mesadactylus fossils have been found in
Colorado.[22]

A somewhat small pterodactyloid with a wingspan of
about 1.8 m (6 ft.) and live mass of about 650 g
(1.4 lbs).[22]
It was the first genus of pterosaur to be known from more than one
site in the formation and is also the Morrison pterosaur scientists
know the most about.[22]
The inarticulated and incomplete remain Dry Mesa find were all that
was known of the genus until the Kingsview find in October, 2002.[22]

The first remains of M. ornithosphyos were discovered in the
1970s in association with the remains of sauropods and other
dinosaurs.[22]
It had many cone-shaped teeth and may have eaten fish.[22]

Geographically present in Oklahoma at Kenton.[23]
An Arizonan trackway generally considered to be from the
Summerville Formation may be Morrison.[23]

The Kenton specimen is kept in the University of Colorado's
Dinosaur Tracks Museum in Denver.[23]
The possible Arizonan Morrison tracks contain the type specimen of
Pteraichnus
saltwashensis, which is kept at the University of Utah.[23]

A rhamphorhynchoid pterosaur with a
wingspan estimated by Peter Wellnhofer to be about 2.5 m.[24]
It was apparently one of the larger Morrison pterosaurs.[24]

A fossil metacarpal was found by O. C. Marsh's crew in the late
1800s and stored in the Yale Peabody Museum.[24]
In 1981 Peter M. Galton erected the
new genus and species to contain it.[24]
However some now consider the single bone too non-diagnostic to
justify the creation of a new taxon.[24]

A small pterodactyloid pterosaur with a
wingspan of about 1 m and an adult mass of only 200g (7
ounces).[25]
The genus is considered to be dubious because it was based on scant
remains; only half of a fourth metacarpal has been found.[25]
The specimen was recovered by a team working for O. C. Marsh during
the bone wars.[25]

For over 100 years it was the only Morrison pterosaur to have
been named.[25]
It also represented the first Jurassic pterosaur found in North
America.[25]